This invention relates to a method and an associated device for removing material internally from a patient. Even more specifically, this invention relates to a thrombectomy device for use with radiology introducer sheaths and catheters.
Clot (thrombus) in the vascular system is a frequently encountered clinical problem in medicine. Obstruction of the human vascular system by clot in both the arterial and venous systems is the cause of much morbidity and mortality.
The location of such clot or other vascular obstructions are usually diagnosed by the performance of an angiogram. During this procedure, dye is injected into the vascular system, permitting the visualization of the vascular tree by fluoroscopic imaging.
In almost all cases of radiological vascular diagnosis or treatment, a device called an "introducer sheath" is used. These sheaths are inserted using a multistage "Seldinger technique" at the beginning of the procedure and they remain in place for the duration of the procedure. They permit guide wires, catheters and various instruments to be repetitively and easily inserted and withdrawn without losing access to the vascular system. Once the sheath is removed it cannot be reinserted without repeating the entire Seldinger technique.
Introducer sheaths frequently incorporate other components to enhance their function. A self sealing "hemostasis valve" permits the insertion of devices into the sheath, and seals around the respective catheters so that bleeding does not occur around them. This valve also closes completely once the catheter has been removed so that bleeding through the sheath is avoided. A "side port" in direct communication with the sheath lumen permits the infusion of saline or other fluids into the body during the performance of the procedure and also permits suction to be transmitted to the sheath lumen.
When clot is identified in the vascular system, one of several approaches may be used depending on clinical indications.
The use of catheters to aspirate clot via suction is perhaps the most intuitive approach. Handley in 1907 was the first to describe such an attempt with clot at the bifurcation of the aorta. In his case report, a suction catheter was threaded upwards through a groin incision, but failed to remove significant amounts of clot. It was subsequently necessary to employ mechanical maceration and forcible saline irrigation in conjunction with the native aortic pressure to expel the clot and restore flow.
The use of suction, applied to a catheter or radiological introducer sheath side port in an attempt to remove clot, is a known clinical maneuver. It is only applicable, however, to partially lysed and "soupy" clot and its success is directly related to the cross sectional internal lumen the sheath or catheter. Even if large-bore catheters (8-12 Fr.) are used, which are undesirable for use in the vascular system, this maneuver is usually only partially successful since clot forms an obstruction at the tip of the sheath or catheter. Despite their size, these catheters need repetitive removal from the body for cleansing secondary to clogging, an option not available for the introducer sheath which must remain in place for the entire procedure.
It should be noted that introducer sheaths and catheters may both be used for the purpose of aspirating clots or other viscous material. Each have their own benefits and disadvantages. Catheters may be withdrawn and cleaned, an option not available with sheaths, while introducer sheaths provide for the largest cross sectional lumen, without being decreased by a catheter inserted through them. The device described herein in accordance with the invention may be used with both, however, it is envisioned for primary use with introducer type sheaths which have the hemostatic valve and side port necessary for optimal use of the device described herein. Of course, the device of the present invention may be complete in itself, with a dedicated outer tube performing functions of the above-discussed introducer sheath.
A March 1996 report by Sharafuddin et al. in the Journal of Vascular and Interventional Radiology describes a method of clot removal through introducer sheaths. A balloon catheter (Fogarty) is used to aid in this process. The balloon catheter is inserted through the sheath and is inflated behind the clot. The balloon is then withdrawn pressurizing and forcing the clot into the sheath, while suction is simultaneously applied to the sheath. This report is significant as it illustrates the heretofore unsolved problems with these techniques that severely limit their applicability. This includes the potentially dangerous maneuver of pressurizing the clot in the vascular vessel in order to effect its removal. Also the procedure is likely to be extremely inefficient because a centrally located and obstructing Fogarty catheter shaft is always located in the path of clot removal.
Previous techniques to remove clot through sheaths, including corkscrew type devices, rods with balls at the tip. etc. have been described. These too are limited by the inevitable obstruction of the tureen by the device rod which will wobble especially at the tip of the sheath. This constant obstruction, at times centrally placed within the introducer sheath, severely limits the efficiency of clot removal through the reduction of the effective cross sectional diameter available for the collection and transportation of clot. Furthermore, it interferes with the ability of the applied suction to catch and draw in a segment of clot since it is difficult to form a seal around this shaft; a necessary condition when entrapping and suctioning clot. Without this seal, blood loss may be increased since blood will be aspirated preferentially instead of the clot.
Because of these inherent and previously insurmountable problems, suction thrombectomy is not a commonly practiced technique in clinical medicine. The challenge remains how to remove clot through relatively small bore tubes (5-7 Fr.) without clogging and without repetitive removal for cleaning.
Besides suction thrombectomy, multiple mechanical methods for clot removal have been proposed. These devices rely on one of several mechanisms to disrupt and macerate clot including rotating baskets, wires, water jets and cutters of various configurations. These devices are all limited by complexity, cost and clot fragment embolization and have not yet found widespread use in clinical medicine.
Because of these limitations, open surgery, clot-lysis via urokinase and long-term treatment with blood thinners remain the primary methods of treatment today for clot in the vascular system. All these modalities have short- and long-term disadvantages.
Certainly a method and device that would enable the extraction of clot through introducer sheaths or simple suction catheters would significantly enhance the treatment options for these patients.